In general, persons wishing to contact a particular party initiate a call to a telephone specifically known to be associated with that party, such as the party's office or wireless telephone. A disadvantage of this method of communication is that parties are not always in close proximity to such associated telephones, or for that matter, in close proximity to any telephone. This presents a problem to persons who need to immediately contact a mobile party, regardless of that party's location.
Several technologies have developed in an effort to solve the problem of establishing communication with a mobile party. These include call forwarding, paging, and cellular systems. However, each of these technologies has drawbacks which prevent seamless and ubiquitous communication.